Airtel — can't recharge with main account balance

I in spite of many mails and visiting airtel store am unable to recharge by airtel prepaid from my main account balance airtel has not replied to my last two mail. The process of trying to recharge has been going on for the past twenty days or so, this amounts to cheating and harassment. Of the customer as i have a balance of more than rs.3000/in my main account balance and surprisingly there is no provision in their app to recharge with main balance and the self care number given in the mail say invalid input against the relevant option number.